OC Farming robot

local component = require("component")
local nav = component.navigation
local directions = { north = 2, south = 3, west = 4, east = 5 }
local robot = require("robot")
local sides = require("sides")
local invControl = component.inventory_controller

function distanceFrom(waypointName)
    local waypoints = nav.findWaypoints(20)
    for i = 1,#waypoints do
        wp = waypoints[i]
        if wp.label:find(waypointName) then
            return table.unpack(wp.position)
        end
    end
end

function goToWaypoint(waypointName)
    x, y, z = distanceFrom(waypointName)
    if (x > 0) then
    local direction = nav.getFacing()
        if (direction == directions.south) then
            robot.turnLeft()
        end
        if (direction == directions.north) then
            robot.turnRight()
        end
        if (direction == directions.west) then
            robot.turnAround()
        end
        while x > 0 do
            if (robot.forward() == true) then
                x = x - 1
            end
        end
    end

    if (z > 0) then
    local direction = nav.getFacing()
        if (direction == directions.west) then
            robot.turnLeft()
        end
        if (direction == directions.east) then
            robot.turnRight()
        end
        if (direction == directions.north) then
            robot.turnAround()
        end
        while z > 0 do
            if (robot.forward() == true) then
                z = z - 1
            end
        end
    end
end

function goHome()
    goToWaypoint("Charger")
end

function faceNorth(direction)
    if (direction == directions.east) then
        robot.turnLeft()
    end
    if (direction == directions.west) then
        robot.turnRight()
    end
    if (direction == directions.south) then
        robot.turnAround()
    end
end

function harvest()
    local direction = nav.getFacing()
    local notEnd = true

    while notEnd do

        local direction = nav.getFacing()
        faceNorth(direction)
        if (direction ~= directions.south) then
            robot.forward()
        end
        robot.forward()
        robot.forward()
        if (direction == directions.south) then
            robot.turnLeft()
        else
            faceNorth(direction)
        end

        for i = 1, 9 do
            robot.useDown()
            if (robot.forward() ~= true) then
                i = i - 1
            end
        end
        local x, y, z = distanceFrom("Path End")
        if (x + y + z == 0) then
            notEnd = false
        end
    end
end

--[[
function sprinkle()
    goToWaypoint("Center")
    robot.select(1)
    for i = 1, 100 do
        robot.place()
        os.sleep(1/20)
    end
end
]]--

function deposit()
    local slot = 1
    for i = 1, 16 do
        robot.select(i)
        while (invControl.dropIntoSlot(sides.top, slot) == false)
        and (invControl.getStackInInternalSlot() ~= nil) do
            slot = slot + 1
        end
    end
end

while true do
    goHome()
    harvest()
    goHome()
    deposit()
    os.sleep(120)
end